With the continuous development of science and technology, varieties of electronic equipment have emerged in abundance. Keyboards are common devices of many electronic equipment, for inputting text information, etc., and commonly are computer keyboards, keyboards of communications equipment and keyboards of household appliances, etc. A membrane switch is a component of the aforesaid keyboards, the development of which now tends towards thin and tight designs, flexibility and low cost and which with advantages such as small size, light weight, simple to operation, etc. Membrane switches have been widely used in various products, for example intelligent electronic instruments, medical instruments, numerical control machine tools, communications equipment, office supplies, home appliances, computer keyboards, etc.
The structure of existing membrane switches mainly consists of three layers, that is, an upper circuit layer, a middle pad layer and a lower circuit layer, and these three layers are independent parts combined to form a membrane switch. The existing membrane switch usually uses materials such as Self-adhesive sticker or double-sided adhesive tape, etc. by screen printing to serve as the middle pad layer for isolation, where a specific mold must be used for holes punching to avoid button positions. However, the following problems are prone to occur in screen printing: uneven adhesive, poor close adaptation, and low product defect-free rate; the double-sided adhesive tape is easily deformed after punching and forming, easily wrinkles and is difficult for operation when bonding, and the membrane switch manufactured has poor waterproof and sealing performance and is easy to be oxidized and corroded, and thus resulting in the instability of the membrane switch.
The Chinese invention patent, Patent Application No. 201010111942.9, discloses a manufacturing method of a membrane switch including the following steps: (1) printing a conductive layer, where electrically conductive silver paste is printed on an upper membrane layer and a lower substrate layer to form an upper conductive layer and a lower conductive layer respectively; (2) printing a pad layer, where UV ink is used to form an UV pad layer by printing the pad layer through printing on the periphery of the key positions of the upper and lower conductive layers, which isolates the upper conductive layer from the corresponding lower conductive layer; (3) bonding the layers, where a glue layer is printed on the area of upper membrane corresponding to the periphery region of the pad of the UV pad layer, leaving the inner region of the UV spacer unprinted and then the glue layer bonds the upper membrane to the corresponding lower substrate layer. By this way, the glue layer bonds the upper membrane with the lower substrate layer at the periphery of the UV pad layer and the periphery of the membrane switch correspondingly to an entirety. Although this manufacturing method of a membrane switch is simple, practical and easy to operate, there is no glue to be printed on the UV pad layer is very difficult to achieve, due to that it is very apt to print the glue on the conductive layers after the upper membrane is printed with the glue and bonded with the UV pad layer, and then affect the contact between the upper and lower conductive layers. In addition, printing of the glue is likely to cause defects such as bubbles and hollow resulting in the membrane switch has quality problems.